(1) Field of the Invention
The present invention relates to tetrazole blowing agents and their derivatives which are used to manufacture foamed thermoplastic resin moldings (hereinafter referred to as the cell structured artificial plastics) which have a high melting point and high softening point, i.e. the tetrazoles and their derivatives are the blowing agents to be used for the cell structured artificial plastics which have high quality and have no shrink and no warp and accordingly have various uses.
(2) Description of the Prior Art
Formerly, as the blowing agents for the manufacture of foamed thermoplastic synthetic resins, liquid hydrocarbons or volatile hydrocarbons such as propane, butane, pentane and heptane or the blowing agents which are decomposed at low temperature such as diazo type blowing agents were used in the fixed molding process.